1. Field of the Invention
This invention relates to regenerative thermal oxidizers and, particularly, a continuous system for purging waste gases from dual heat exchange beds associated with a regenerative thermal oxidizer.
2. Description of Prior Art
Regenerative incinerator systems are used to treat waste gases containing volatile organic compounds (VOC's), which are preferably incinerated before exhausting the treated waste gases to the atmosphere. Additionally, regenerative incinerator systems serve to eliminate undesirable odors present in untreated waste gases before venting to the atmosphere.
Regenerative incinerator systems typically include regenerative thermal oxidizers and waste gas purge recovery tanks as part of the combustion cycle. The purge recovery tank or other similar means is used to collect untreated waste between combustion cycles of the system. The concept of collecting untreated waste gases from heat exchange beds associated with a regenerative thermal oxidizer into a purge recovery tank between combustion cycles is well known. It is also common to recycle these untreated waste gases to the regenerative thermal oxidizer to complete their incineration. One such system is disclosed in U.S. Pat. No. 3,870,474 to Houston.
The Houston patent teaches using a partially evacuated surge chamber with suitable valving to collect contaminated air from a regenerative incinerator, when the air flow through the regenerative incinerator is reversed. A check valve prevents outside air from entering the surge chamber while contaminated air is being drawn into the surge chamber from the regenerative incinerator. A vacuum pump or other similar means is used to remove the contaminated air from the surge chamber. The evacuated contaminated air from the surge chamber is recycled back to the inlet for the regenerative incinerator and into a combustion chamber to complete the incineration of the contaminates contained in the waste gases. The purified air is then mixed with the main air flow for discharge from the system to the atmosphere.
The arrangement disclosed by Houston is a closed system. One of the drawbacks with a closed system is that pressure is permitted to build in the purge recovery tank between combustion cycles of the regenerative thermal oxidizer. Additionally, a vacuum pump or other similar means is required to empty the contents of the surge chamber and recycle any untreated waste gases for re-combustion. Further, a check valve is required to prevent the drawing in of atmospheric air through a vent stack when the vacuum pump is activated. This additional equipment leads to unnecessary costs, space requirements and maintenance.
U.S. Pat. No. 4,741,690 to Heed teaches a similar method for treating waste gases. The Heed patent discloses an arrangement having a storing device for receiving untreated waste gases from a combustor and two check valves to prevent the escape of untreated waste gases from the system. The arrangement taught by the Heed patent requires a fan to empty the contents of the storage device and reintroduce purged, untreated waste gases to the combustor.
It is therefore an object of the invention to overcome the above-discussed disadvantages by providing a continuous open system for the removal of waste gases from a regenerative thermal oxidizer having two (2) heat exchange beds.
It is a further object of the invention to provide a second, compact embodiment which provides savings in material costs and enhances the overall thermal efficiency of the regenerative thermal oxidizer.